1. Field of the Invention
The present invention relates to an access optical communication network, and more particularly, to the structure of an optical communication network using a passive element between subscribers and a central office of a network provider.
2. Description of the Related Art
While up-to-date optical communication technology is applied to a backbone network, a coaxial cable is the main communication means for an access network, i.e. for data communication between a remote node and a typical home or an office, still testing optical communication.
However, since many subscribers use the access network, it is estimated that a large optical communication market will form when the access network technology matures, and thus much research has been carried out to preoccupy technologies necessary for forming the large optical communication market and to secure intellectual property rights.
The strongest scheme researched as a communication means for the access network is a wavelength division multiplexing passive optical network (WDM-PON) supporting a method of simultaneously passing several channels allocated to a plurality of optical wavelengths through a single optical fiber using a passive element.
The present invention traces wavelength optical signals carried on channels in a WDM-PON by switching channels using wavelength tunable lasers and combining a time division multiplexing (TDM) concept to the channel transmission method, thereby increasing the transmission efficiency.
In “Spectral slicing WDM-PON using wavelength-seeded reflective SOAs,” IEE Electron. Lett., Vol. 37, No. 19, pp 1181-1182, 2001, reported by P. Healey et al, which is one of the representative WDM-PON structures that have been suggested or reported, a method of spectrally slicing light of an erbium doped fiber amplifier (EDFA) or a light emitted diode (LED) into a plurality of wavelengths using an arrayed waveguide grating (AWG), allocating channels to the wavelengths, amplifying the channel-allocated wavelengths using a reflective semiconductor optical amplifier (RSOA), and modulating the amplified wavelengths to generate a data signal and then transmitting the generated data signal was suggested, and a test result obtained by transmitting data signals of 8 channels of 1.25 GHz over a distance of 25 Km using the method was reported.
In “A Low-cost WDM source with an ASE injected Fabry-Perot semiconductor laser,” IEEE Photon. Technol. Lett., Vol. 12, No. 8, pp. 1067-1069, 2000, reported by Hyun Deok Kim. et al, which is another one of the representative WDM-PON structures that have been suggested or reported, a method of generating a data signal by slicing light of a light source into a plurality of wavelengths and inputting the wavelengths to a wavelength selectable Fabry-Perot laser diode (FP-LD) was suggested, and a test result obtained by transmitting the data signal at 155 Mbps over a distance of 120 Km using the method was reported.
In addition, in “LARNet, a Local Access Router Network,” IEEE Photon. Technol. Lett., Vol. 7, No. 2, pp. 215-217, 1995 reported by M. Zirngibl. et al, a method of forming a multifrequency laser (MFL) by engraving a distributed Bragg reflector (DBR) grating in each channel waveguide of an AWG and generating a data signal using the MFL was suggested, and a test result obtained by transmitting data signals of 9 channels at 200 Mbps over a distance of 10 Km using the method was reported.
The conventional methods described above do not suggest any improvement of a transmission rate through channel switching and wavelength tracing functions, as suggested in the present invention. Thus, a channel switching method and system for improving the transmission efficiency through the channel switching and wavelength tracing function in a WDM-PON will be suggested in the present invention.